Recently, as a new memory device, a nonvolatile semiconductor memory device called RRAM (Resistance Random Access Memory) is noted. The RRAM uses a resistance memory element which can memorize a plurality of resistance states of different resistance values, which are changed by electric stimulations applied from the outside and whose high resistance state and low resistance state are corresponded to, e.g., information “0” and “1” to be used as a memory element. The RRAM highly potentially has high speed, large capacities, low electric power consumption, etc. and is considered prospective.
The resistance memory element has a resistance memory material whose resistance states are changed by the application of voltages sandwiched between a pair of electrodes. As the typical resistance memory material, oxide materials containing transition metals are known.
The nonvolatile semiconductor memory device using the resistance memory element is disclosed in, e.g., International Publication No. WO97/05665, U.S. Pat. No. 6,872,963, A. Beck et al., Appl. Phys. Lett., Vol. 77, p. 139 (2001), W. W. Zhuang et al., Tech. Digest IEDM 2002, p. 193, and I. G. Baek et al., Tech. Digest IEDM 2004, p. 587.